Existing power converters receive a single input and output a single output. However, as power sources or loads become more diverse, the need to generate a plurality of outputs in response to a plurality of inputs (which are input at various times) is becoming desirable. Particularly, in the field of a power converters mounted in vehicles, various control units have been integrated, and multi-input multi-output devices are becoming more desirable.
FIG. 18 illustrates a power converter that controls loads of two systems as an example of a vehicle lighting device having a plurality of light sources. The power converter receives a power 1 directly connected to a vehicle battery BT. A controller area network (CAN) communication 2 which is a vehicle communication controller, controls a light emitting diode (LED) 3 (reading light) and an LED 4 (foot light) of two systems. The respective inputs are received by an input connection unit 10, and an output is output to the LEDs 3 and 4 of two systems via an output connection unit 11. The power converter is configured to include first and second power converting units 8 and 9 for converting a voltage of the battery directly-connected power 1 into a certain current required by the LEDs 3 and 4, a control unit 7 for controlling the first and second power converting units 8 and 9, a control power supply unit 5 that receives the battery directly-connected power 1 and outputs the power 1 to the control unit 7, and a transceiver 6 that receives the CAN communication 2 notifying lighting timing of the LEDs 3 and 4. The control unit 7 controls the LEDs 3 and 4 by receiving detection signals corresponding to output current values from the first and second power converting units 8 and 9 and outputting driving signals to the first and second power converting units 8 and 9.
FIGS. 19 and 20 illustrate the first power converting unit 8 and the second power converting unit 9, respectively. FIG. 19 illustrates a configuration of a flyback circuit which is an example of the power converting unit. A direct current (DC) power (a voltage between +B and GND) is received by a condenser C1, and a series circuit of a primary side winding TP1 of a transformer T1 and a switch element SW1 is connected in parallel to the condenser C1. A driving signal of the switch element SW1 is input to the power converting unit. A series circuit of a secondary side winding TS1 of the transformer T1 and a diode D1 are connected in parallel to a condenser C2. An output unit is installed to connect a series circuit of a load and a resistor R1 in parallel to the condenser C2. An output current is detected by the resistor R1 and output as the detection signal.
A description will be made below in connection with a circuit operation. A current flows from the condenser C1 to the primary side winding TP1 of the transformer T1 and the switch element SW1 at ON timing of the switch element SW1. A direction of the diode D1 at the secondary side is set to a direction in which a secondary side current does not flow when the switch element SW1 is turned on, so that energy is accumulated in the transformer T1. The energy accumulated in the transformer T1 moves from the secondary side winding TS1 of the transformer T1 to the condenser C2 via the diode D1 at OFF timing of the switch element SW1. Power is supplied from the condenser C2 to the load via the resistor R1. An output current is detected by the resistor R1, and the control unit 7 adjusts an ON/OFF time of the driving signal of the switch element SW1. Thus, the output current can be constantly controlled.
FIG. 20 illustrates a configuration of a boosting circuit using an auto transformer which is an example of the power converting unit. A DC power (a voltage between +B and GND) is received by a condenser C3, and a series circuit of a primary side winding TP2 of a coil T2 and a switch element SW2 is connected in parallel to the condenser C3. A driving signal of the switch element SW2 is input to the power converting unit. A secondary side winding TS2 of the transformer T2, a diode D2, and a condenser C4 are connected in series to one another and in parallel to the switch element SW2. The primary side winding TP2 and the secondary side winding TS2 of the coil T2 are wounded to have an additive polarity, and the diode D2 is installed in a direction in which a current flows from the power to the output side. An output unit is installed to connect a series circuit of a load and a resistor R2 in parallel to the condenser C4. An output current is detected by the resistor R2, and the detected output signal is output as a detection signal.
A description will be made below in connection with a circuit operation. A current flows from the condenser C3 to the primary side winding TP2 of the coil T2 and the switch element SW2 at ON timing of the switch element SW2, and energy is accumulated in the coil T2. The energy accumulated in the coil T2 moves to the condenser C4 via the condenser C3, the coil T2, and the diode D2 at OFF timing of the switch element SW2. Power is supplied from the condenser C4 to the load via the resistor R2. An output current is detected by the resistor R2, and the control unit 7 adjusts an ON/OFF time of the driving signal of the switch element SW2. Thus, the output current can be constantly controlled.
FIG. 21 illustrates a power converter having a different configuration for controlling loads of two systems. What is different from FIG. 18 in the aspect of input and output is that DC power as an input includes Acc power 12 linked with an accessory Acc of a vehicle and IGN power source 13 linked with the ignition (IGN) of the vehicle. For this reason, the Acc power 12 and the IGN power source 13 are input to a control power supply unit 5 via diodes D4 and D3, respectively. Further, a power converting unit includes a predetermined current circuit (which has a current value obtained by dividing a voltage value, obtained by subtracting a forward voltage drop Vf of a load 3 from the IGN power source 13, by resistance of the resistor R3) configured with a resistor R3 and a switch element SW3 and a constant current circuit configured with a coil L1, a diode D5, a switch element SW4, a current detecting resistor R4, and a detecting unit 14.
FIG. 22 illustrates an operation of the constant current circuit. When the switch element SW4 is turned on, a current from the Acc power 12 flows through the coil L1, the LED 4, the current detecting resistor R4, and the switch element SW4. When the current value becomes a predetermined current Imax, the switch element SW4 is turned off. When the switch element SW4 is turned off, a current of the coil L1 flows through the LED 4, the current detecting resistor R4 and the diode D5. When the current value becomes a predetermined current value Imin, the switch element SW4 is turned on. This operation is repeated, so that constant current control is implemented.
The control unit 7 that controls a plurality of loads usually controls the switch elements SW3 and SW4 according to the CAN communication 2 or other communications and supplies power to the loads 3 and 4 (for example, the LEDs 3 and 4).